In a communication system in which a TDMA/TDD (Time Division Multiple Access/Time Division Duplexing) scheme is adopted, such as PHS (Personal Handyphon System) and XGP (eXtended Global Platform) also called next-generation PHS, a base station may adopt an adaptive array antenna scheme of adaptively controlling the directivity of an array antenna composed of a plurality of antennas. Patent Documents 1 and 2 disclose the technique regarding the adaptive array antenna scheme. The base station adopting the adaptive array antenna scheme controls the reception directivity and transmission directivity of the array antenna based on a known signal from a communication terminal.